misc: Further improve imports styling

By introducing `imports_granularity="Module"` format strategy,
effectively groups imports from the same module into one line or block,
improving maintainability and readability.

Signed-off-by: Ruoqing He <heruoqing@iscas.ac.cn>

rate_limiter/src/lib.rs

@@ -520,8 +520,7 @@ impl Default for RateLimiter {
 
 #[cfg(test)]
 pub(crate) mod tests {
-    use std::fmt;
-    use std::thread;
+    use std::{fmt, thread};
 
     use super::*;